Cob Re[2]: Ener-Grid Revisited

[EREC - Duncan, Cameron]

>>     If you investigate the Rastra/Ener-Grid product, you will find the
>>reputed R-35.5 that the company projects was performed by Braun   
Intertec.
>>This reputable certified lab repeated the tests before releasing the
>>report to confirm the numbers. A subsequent test by the Construction
>>Technology Laboratory found the assembly to yield only an overall   
R-value
>>of about R-6 to R-8 (R-1.41 per inch).
...
>    Wow!  How on earth do they explain a disparity like that?
>-Speireag.
...
Speirag & Michael,
     To directly answer your question, I don't know.
History:
     Initially a German product, it came to the US in the 1980s as   
"Rastra." The company renamed itself (and product) Ener-Grid in 1994   
(Energy Design Update, (15:4) pp. 7-8, April 1995).
     UL performed fire tests on an Ener-Grid wall in Chicago in 1991   
using ASTM E119 procedure--wall loaded with 20k lbs/sf pressure, one side   
exposed to 2k degF temp., unexposed side temp. measurements taken over 2   
hr. time period (passes test if temp. rise is less than 300 degF). It   
raised only 1 degF--"very unusual" claimed UL staff.
     Geoscience Laboratory reportedly was the first to test the thermal   
resistance of the material years ago. They refused to release their   
results because they found them unbelievable.
     In January 1995, Portland's Braun Intertec was commissioned to test   
the material. The Braun technicians, also finding it difficult to believe   
their results, repeated their test for confirmation purposes. They only   
released their results once their subsequent testing matched their   
initial values.
     This report sent a wave of astonishment through the building science   
community. The best explanation for the high R-value was that "the   
low-density mixture of polystyrene and cement somehow behaves in a way   
that is not explainable by conventional engineering principles (Energy   
Design Update, (16:10) pp. 8-9, October 1996)."
...
     We receive inquiries from occasional potential customers, but I've   
not heard of any being voluntarily informed of Construction Technology   
Laboratory's (CTL) report from Ener-Grid personnel. Other than the   
R-value, I am concerned about the potential for insect attack. Since the   
concrete-coated polystyrene beads are shaped into a connecting web from   
the material's outer wall to it's inner wall, it may serve as a conduit   
for infestation if susceptible to tunneling as is conventional   
polystyrene.
     If anyone tests a sample of the material (for insect intrusion,   
fire, acoustics, effects on people with allergies, etc.), I'd love to   
hear of your results, empirical or otherwise. Thanks.

Cameron Duncan
EREC Architect, Technical Specialist
CDUNCAN at nciinc.com
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